1. Field of the Invention
The present invention relates to a lens barrel which incorporates a motor such as a vibrating motor.
2. Description of the Related Art
Vibrating motors which operate on a principle quite different from that of conventional electromagnetic motors have been developed recently, and researches on the practical applications of such vibrating motors in various fields have been conducted. Such applications include the use of a vibrating motor in an optical device such as a camera, specifically a lens barrel.
FIG. 4 is a schematic cross-sectional view of a lens barrel incorporating an annular vibrating motor M, upon which the present invention is based. In FIG. 4, a reference numeral 1 denotes a fixed, double-skinned cylinder having an inner cylindrical portion 1a, a reference symbol M denotes an annular vibrating motor fitted on the outer peripheral surface of the inner cylindrical portion la, and a reference numeral 15 denotes a bearing for supporting a rotor of the motor M.
The vibrating motor M is composed of an annular vibrating member 2 which is a ring having a trapezoidal cross-section, an electrostrictive element 2a formed integrally with the vibrating member 2, an annular rotor 3 pressing against the end surface of the vibrating member 2, an annular felt 5 pressing against the end surface of the electrostrictive element 2a, an annular felt base 6 to which the felt 5 is fixed, an annular belleville spring 4 for pressing the vibrating member 2 toward the end surface of the rotor 3, and so on.
The bearing 15 is coupled to the rotor 3 with a vibration absorbing member 7 therebetween. The bearing 15 is composed of an outer rotating ring 9 having a spherical member rolling surface on its inner peripheral surface, an inner fixed ring 1b formed by the distal end portion of the inner cylindrical portion 1a of the fixed cylinder 1, and spherical members 8 disposed between the outer rotating ring 9 and the inner fixed ring 1b.
A rotating cylinder 11 having a threaded portion 11a on an inner peripheral surface thereof is coupled to the outer rotating ring 9 of the bearing 15, so that the rotation cylinder can be rotated around an axis Z of the motor 2 together with the outer rotating ring 9.
A lens holder 12 for holding a lens L has on an outer peripheral surface thereof a threaded portion 12a, which is in threaded engagement with the threaded portion 11a formed on the inner peripheral surface of the rotating cylinder 11. In consequence, rotation of the rotating cylinder 11 moves the lens holder 12 in a direction parallel to the axis Z. A groove 12b is formed on the outer peripheral surface of the lens holder 12 parallel to the axis Z. A key or rotation suspending member 14, having an L-shaped form and mounted on the fixed cylinder 1, is fitted into the groove 12b in such a manner as to be movable relative to the lens holder 12 in the direction of axis Z.
The thus-arranged lens barrel shown in FIG. 4 incorporates as the motor bearing a spherical bearing member 8. Hence, manufacture of the bearing requires troublesome work and the production cost thereof is high.